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###Option 1

Using the deprecated GROUP BY ALL syntax:

SELECT 
    AODAR.fkSiteID,
    NumChecks =
        ISNULL
        (
            SUM(AODAR.SearchTypePerson) + 
            SUM(AODAR.SearchTypeLocker) + 
            SUM(AODAR.SearchTypeSpotRandom) + 
            SUM(AODAR.SearchTypePersVehicle) + 
            SUM(AODAR.SearchTypeVisitorContractorVehicle) + 
            SUM(AODAR.SearchTypeCompanyVehicle) + 
            SUM(AODAR.SearchTypeToilet) + 
            SUM(AODAR.PatrolExternal) + 
            SUM(AODAR.PatrolCarPark) + 
            SUM(AODAR.PatrolPerimeter) + 
            SUM(AODAR.PatrolInternal) + 
            SUM(AODAR.VehicleCheckAmbientLine) + 
            SUM(AODAR.VehicleCheckFridgeLine) + 
            SUM(AODAR.VehicleCheckSealChecks) + 
            SUM(AODAR.OtherChecksIDCards) + 
            SUM(AODAR.OtherChecksIncidentReports) + 
            SUM(AODAR.OtherChecksColdStoreChecks)
            , 0
        )
FROM dbo.AAHOfficerDailyActivityReport AS AODAR
WHERE 
    AODAR.MonthOfReport = 6 
    AND AODAR.RecordIsDeletedYN = 0
GROUP BY ALL 
    AODAR.fkSiteID
HAVING 
    AODAR.fkSiteID IN (945,947,948,949,950,951,952)
ORDER BY
    AODAR.fkSiteID;

###Option 2

Or equivalently, without the deprecated syntax:

SELECT 
    AODAR.fkSiteID,
    NumChecks =
        SUM(AODAR.SearchTypePerson) + 
        SUM(AODAR.SearchTypeLocker) + 
        SUM(AODAR.SearchTypeSpotRandom) + 
        SUM(AODAR.SearchTypePersVehicle) + 
        SUM(AODAR.SearchTypeVisitorContractorVehicle) + 
        SUM(AODAR.SearchTypeCompanyVehicle) + 
        SUM(AODAR.SearchTypeToilet) + 
        SUM(AODAR.PatrolExternal) + 
        SUM(AODAR.PatrolCarPark) + 
        SUM(AODAR.PatrolPerimeter) + 
        SUM(AODAR.PatrolInternal) + 
        SUM(AODAR.VehicleCheckAmbientLine) + 
        SUM(AODAR.VehicleCheckFridgeLine) + 
        SUM(AODAR.VehicleCheckSealChecks) + 
        SUM(AODAR.OtherChecksIDCards) + 
        SUM(AODAR.OtherChecksIncidentReports) + 
        SUM(AODAR.OtherChecksColdStoreChecks)
FROM
(
    SELECT
        AODAR.fkSiteID,
        AODAR.SearchTypePerson,
        AODAR.SearchTypeLocker,
        AODAR.SearchTypeSpotRandom,
        AODAR.SearchTypePersVehicle,
        AODAR.SearchTypeVisitorContractorVehicle,
        AODAR.SearchTypeCompanyVehicle,
        AODAR.SearchTypeToilet,
        AODAR.PatrolExternal,
        AODAR.PatrolCarPark,
        AODAR.PatrolPerimeter,
        AODAR.PatrolInternal,
        AODAR.VehicleCheckAmbientLine,
        AODAR.VehicleCheckFridgeLine,
        AODAR.VehicleCheckSealChecks,
        AODAR.OtherChecksIDCards,
        AODAR.OtherChecksIncidentReports,
        AODAR.OtherChecksColdStoreChecks
    FROM dbo.AAHOfficerDailyActivityReport AS AODAR
    WHERE 
        AODAR.MonthOfReport = 6 
        AND AODAR.RecordIsDeletedYN = 0
        AND AODAR.fkSiteID IN (945,947,948,949,950,951,952)

    UNION ALL

    SELECT
        AODAR.fkSiteID,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
    FROM dbo.AAHOfficerDailyActivityReport AS AODAR
    WHERE 
        AODAR.fkSiteID IN (945,947,948,949,950,951,952)
) AS AODAR
GROUP BY
    AODAR.fkSiteID
ORDER BY
    AODAR.fkSiteID;

Results:

╔══════════╦═══════════╗
║ fkSiteID ║ NumChecks ║
╠══════════╬═══════════╣
║      945 ║       228 ║
║      947 ║        27 ║
║      948 ║         0 ║
║      949 ║        58 ║
║      951 ║        67 ║
║      952 ║      1015 ║
╚══════════╩═══════════╝

db<>fiddle demo

###OPtion 3

Or, if you really intended 950 to be in the results even though it does not appear in the data set:

SELECT
    Sites.fkSiteID,
    NumChecks = ISNULL(Totals.NumChecks, 0)
FROM 
 (
    VALUES
        (945),
        (947),
        (948),
        (949),
        (950),
        (951),
        (952)
 ) AS Sites (fkSiteID)
LEFT JOIN
(
    SELECT
        AODAR.fkSiteID,
        NumChecks =
            SUM(AODAR.SearchTypePerson) + 
            SUM(AODAR.SearchTypeLocker) + 
            SUM(AODAR.SearchTypeSpotRandom) + 
            SUM(AODAR.SearchTypePersVehicle) + 
            SUM(AODAR.SearchTypeVisitorContractorVehicle) + 
            SUM(AODAR.SearchTypeCompanyVehicle) + 
            SUM(AODAR.SearchTypeToilet) + 
            SUM(AODAR.PatrolExternal) + 
            SUM(AODAR.PatrolCarPark) + 
            SUM(AODAR.PatrolPerimeter) + 
            SUM(AODAR.PatrolInternal) + 
            SUM(AODAR.VehicleCheckAmbientLine) + 
            SUM(AODAR.VehicleCheckFridgeLine) + 
            SUM(AODAR.VehicleCheckSealChecks) + 
            SUM(AODAR.OtherChecksIDCards) + 
            SUM(AODAR.OtherChecksIncidentReports) + 
            SUM(AODAR.OtherChecksColdStoreChecks)
    FROM dbo.AAHOfficerDailyActivityReport AS AODAR
    WHERE
        AODAR.MonthOfReport = 6 
        AND AODAR.RecordIsDeletedYN = 0
    GROUP BY 
        AODAR.fkSiteID
) AS Totals
    ON Totals.fkSiteID = Sites.fkSiteID
ORDER BY
    Sites.fkSiteID;

The following code produces the results you want by outer joining the list of sites that must appear in the output, with the results of your data query grouped by site id.

SELECT
    Sites.fkSiteID,
    NumChecks = ISNULL(Totals.NumChecks, 0)
FROM (VALUES (945),(947),(948),(949),(950),(951),(952)) AS Sites (fkSiteID)
LEFT JOIN
(
    SELECT
        AODAR.fkSiteID,
        NumChecks =
            SUM(AODAR.SearchTypePerson) + 
            SUM(AODAR.SearchTypeLocker) + 
            SUM(AODAR.SearchTypeSpotRandom) + 
            SUM(AODAR.SearchTypePersVehicle) + 
            SUM(AODAR.SearchTypeVisitorContractorVehicle) + 
            SUM(AODAR.SearchTypeCompanyVehicle) + 
            SUM(AODAR.SearchTypeToilet) + 
            SUM(AODAR.PatrolExternal) + 
            SUM(AODAR.PatrolCarPark) + 
            SUM(AODAR.PatrolPerimeter) + 
            SUM(AODAR.PatrolInternal) + 
            SUM(AODAR.VehicleCheckAmbientLine) + 
            SUM(AODAR.VehicleCheckFridgeLine) + 
            SUM(AODAR.VehicleCheckSealChecks) + 
            SUM(AODAR.OtherChecksIDCards) + 
            SUM(AODAR.OtherChecksIncidentReports) + 
            SUM(AODAR.OtherChecksColdStoreChecks)
    FROM dbo.AAHOfficerDailyActivityReport AS AODAR
    WHERE
        AODAR.MonthOfReport = 6 
        AND AODAR.RecordIsDeletedYN = 0
    GROUP BY 
        AODAR.fkSiteID
) AS Totals
    ON Totals.fkSiteID = Sites.fkSiteID
ORDER BY
    Sites.fkSiteID;

Or equivalently:

###Option 1

###Option 2

Or equivalently, without the deprecated syntax:

###OPtion 3

Or, if you really intended 950 to be in the results even though it does not appear in the data set:

SELECT
    Sites.fkSiteID,
    NumChecks = ISNULL(Totals.NumChecks, 0)
FROM 
(
    VALUES
        (945),
        (947),
        (948),
        (949),
        (950),
        (951),
        (952)
) AS Sites (fkSiteID)
LEFT JOIN
(
    SELECT
        AODAR.fkSiteID,
        NumChecks =
            SUM(AODAR.SearchTypePerson) + 
            SUM(AODAR.SearchTypeLocker) + 
            SUM(AODAR.SearchTypeSpotRandom) + 
            SUM(AODAR.SearchTypePersVehicle) + 
            SUM(AODAR.SearchTypeVisitorContractorVehicle) + 
            SUM(AODAR.SearchTypeCompanyVehicle) + 
            SUM(AODAR.SearchTypeToilet) + 
            SUM(AODAR.PatrolExternal) + 
            SUM(AODAR.PatrolCarPark) + 
            SUM(AODAR.PatrolPerimeter) + 
            SUM(AODAR.PatrolInternal) + 
            SUM(AODAR.VehicleCheckAmbientLine) + 
            SUM(AODAR.VehicleCheckFridgeLine) + 
            SUM(AODAR.VehicleCheckSealChecks) + 
            SUM(AODAR.OtherChecksIDCards) + 
            SUM(AODAR.OtherChecksIncidentReports) + 
            SUM(AODAR.OtherChecksColdStoreChecks)
    FROM dbo.AAHOfficerDailyActivityReport AS AODAR
    WHERE
        AODAR.MonthOfReport = 6 
        AND AODAR.RecordIsDeletedYN = 0
    GROUP BY 
        AODAR.fkSiteID
) AS Totals
    ON Totals.fkSiteID = Sites.fkSiteID
ORDER BY
    Sites.fkSiteID;

Results:

╔══════════╦═══════════╗
║ fkSiteID ║ NumChecks ║
╠══════════╬═══════════╣
║      945 ║       228 ║
║      947 ║        27 ║
║      948 ║         0 ║
║      949 ║        58 ║
║      950 ║         0 ║
║      951 ║        67 ║
║      952 ║      1015 ║
╚══════════╩═══════════╝

db<>fiddle demo